The present invention relates to a cooling apparatus for electronic systems, and in particular to a cooling apparatus which utilizes liquid coolant so as to cool, one by one, electronic parts such as semiconductor devices, a CPU, an FET and a power amplifier, which are used in an electronic circuit within an electronic system.
Several circuit boards are densely installed in a housing rack of an electronic system such as an electronic computer or a broad casting system, and they are mounted thereon with electronic parts including semiconductor devices, a CPU, a FET and a power amplifier, which generate high heat power Accordingly, a cooling apparatus is required for cooling the electronic system. Electronic parts generating high temperature heat, such as electronic devices, a CPU and a power amplifier, are effectively operated in a narrow temperature range, and accordingly, they have to be individually cooled, instead of cooling the electronic system in its entirety. Accordingly, in a cooling apparatus for an electronic system, these years, electronic parts are located, adjacent to a cooling pipe through which liquid coolant flows in order to cool them.
For example, JP-U-2-28965, JP-A-63-131469 and JP-A-6-304739, propose such a configuration that a flattened cooling pipe which meanders is attached to a water-cooled cooling plate on which electronic parts are mounted so as to increase the thermal contact area between the cooling plate and the cooling pipe in order to enhance the cooling efficiency. With this configuration, in order to efficiently transfer heat generated from the electronic part to the flattened cooling pipe, the oblateness of the flattened cooling pipe is increased so as to increase the thermal transfer cross-sectional area between the electronic part and the flatted cooling pipe. For example, the width of the flattened cooling pipe is widened up to a value which is equal to or greater than the width of the electronic part. However, if several electronic parts are arrayed, the flattened cooling pipe should successively be bent so as to meander along the electronic parts which are densely mounted on a circuit board, and accordingly, the radii of curvature with which the flattened cooling pipe is bent must be smaller. In general, bending a flattened pipe having a high oblateness to a small radius of curvature is extremely difficult in comparison with bending a flattened pipe having a small oblateness in view of the manufacture thereof. Further, if has been found, the higher the oblateness, the larger the pressure loss of the flattened cooling pipe.
Meanwhile, if the oblateness of the flattened cooling pipe is restrained to be small, the radius of curvature of the flattened cooling pipe would be decreased. However, the heat transfer cross-sectional area (thermal contact area) between the electronic part and the flattened cooling pipe becomes smaller, thereby enhancement of the cooling capacity for the electronic part is restricted.
Thus, successively bending the flattened cooling pipe having a high oblateness so as to cope with an array of electronic parts which are densely mounted causes restriction to any of enhancement of cooling efficiency, enhancement of the productivity of the flattened cooling pipe and reduction of pressure loss in the flattened cooling pipe.
Further, the cooling apparatus for an electronic system, dewing is likely to occur around a cooling pipe through which liquid coolant flows, and an electronic part to be cooled in view of a relationship between a temperature and a humidity of an environment surrounding them. This dewing would cause inferior insulation, deterioration of the electronic part, inferior contact of a connector and the like. Further, in a cold season, when the temperature of the environment around the electronic system, such as, the atmospheric temperature is lowered, liquid coolant which carries out heat-exchange with the environment through the intermediary of a heat-exchanger is frozen, causing fracturing of the cooling pipe, or lowering of the performance of the electronic part. That is, it is required to control the temperature of the electronic part with the use of a cooling apparatus in order to efficiently operate the electronic part within a relatively narrow effective operating temperature range.
JP-A-6-164178 proposes a cooling apparatus that detects a humidity of the environment surrounding electronic parts in an electronic system and computes a supply temperature of liquid coolant which can prevent dewing so as to control this supply temperature.
JP-A-5-75284 proposes a cooling apparatus which carries out heat-exchange between coolant and an atmosphere in an electronic system when the difference between a temperature of the coolant and a temperature of the atmosphere in the electronic system becomes equal to a predetermined value during deenergization of the electronic parts, in order to prevent dewing during a start of operation of the electronic system.
JP-B2-2656581 discloses a cooling apparatus that measures an atmospheric temperature in an electronic system and a temperature of liquid coolant, and detects dewing around a cooling pipe in the cooling apparatus by means of a dew sensor in order to surely prevent dewing around the cooling pipe.
Further, JP-B2-2508640 discloses a cooling apparatus which controls turn-on and -off operation of a plurality of heat-exchanger units having different cooling capacities in accordance with a difference between a supply side temperature and a return side temperature of liquid coolant, and a difference between an atmospheric temperature in an electronic system and the supply side temperature of the liquid coolant in order to carry out efficient cooling.
As stated above, in the cooling apparatus using liquid coolant, the capacity of the heat-exchanger unit is set so as to obtain a temperature range in which electronic parts including semiconductor devices, an FET, a CPU and a power amplifier efficiently function. Since the heat-exchanger unit introduces the atmospheric air and carries out heat-exchange between the atmospheric air and liquid coolant so as to cool the liquid coolant, the liquid coolant is excessively cooled as the temperature of the atmospheric air lowers, causing problems of excessive consumption of power, freezing and dewing.
Further, in an unmanned broadcasting system, a plurality of parallel electronic systems are in general provided in order to enhance the reliability, one of which is used as a living system for usual operation while the other of which is used as a stand-by system that is adapted to operate if the living system malfunctions. Further, in an electronic apparatus, a plurality of electronic systems are operated, independent from one other, and accordingly, there may be such a case that one of the electronic system is operated but the other rests. In this apparatus, the electronic systems are incorporated with cooling apparatuses, respectively, and if one of the electronic system rests, the corresponding cooling apparatus also rests. Accordingly, in the electronic system on resting, since liquid coolant stagnates, it is required to prevent the liquid coolant from being frozen when the temperature of ambient air lowers. Thus, anti-freezing fluid is in general used as liquid coolant. This anti-freezing fluid causes possible corrosion of a part of the cooling pipe or that of a tank with which the anti-freezing fluid makes contact. Further, handling of the anti-freezing fluid requires consideration fully to the environment. Further, should the liquid coolant having a low temperature pass through the electronic system which has a high temperature, and which is started from a rest condition, there would be caused a problem of dewing as mentioned above. Thus, it is required to maintain the temperature of the liquid coolant at a temperature higher than the dewing temperature. Thus, it is desirable to always heat liquid coolant in the system on resting by means of a heater or the like or to operate all electronic systems at the same time. Thus, relatively large power consumption is required to avoid lowering the temperature of the liquid coolant below the dewing temperature.
JP-A-9-298377 discloses a cooling apparatus having a plurality of heat-exchanger units which are provided in a plurality of housings accommodating therein electronic circuits, wherein an atmosphere is led from a first housing into a heat-exchanger unit belonging to a second housing through a duct so as to cool the atmosphere in this heat-exchanger unit in order to cool electronic circuits in the second housing, thereby to reduce the volume of blowing air in total.
Further, heaters are provided respectively in tanks in a plurality of cooling systems, which are intermittently energized in order to warm up liquid coolant for an electronic system on resting, that is, for a stand-by electronic system, and pumps in the cooling systems are intermittently operated in order to prevent occurrence of freezing and dewing.
However, such intermittent operation of the pumps and intermittent operation of the heaters in the tanks within the cooling systems would cause problems of deterioration of the function of the pumps, increase of the consumption power and the like.
The present invention is devised in order to eliminate the above-mentioned problems to inherent to the above-mentioned prior art, and accordingly, a first object of the present invention is to provide a cooling apparatus for an electronic system, in which a cooling pipe having a high oblateness is laid along positions corresponding to several electronic parts densely mounted in an electronic system, having curved parts each formed of a circular pipe with a small radius of curvature, thereby aim at enhancing the cooling function for several electronic parts, reducing pressure loss and enhancing the productivity of the cooling pipe.
Further, a second object of the present invention is to provide a cooling apparatus for an electronic system, which controls the heat-exchange capacity of a heat-exchanger unit in accordance with an ambient temperature so as to stably maintain an operating temperature of the electronic parts, irrespective of an ambient temperature, and to aim at saving energy while the effective operating temperature is maintained.
Further, a third object of the present invention is to provide a cooling apparatus for a plurality of electronic systems, which can enhance the reliability of the cooling apparatus itself and aim at saving energy.
A fourth object of the present invention is to provide a cooling apparatus for a plurality of electronic systems, in which liquid coolant in a cooling system on operation (a living system) is led into a stand-by cooling system (a back-up system) on resting so as to allow the temperature of liquid coolant in the stand-by cooling system (back-up system) on resting to approach that of the liquid coolant in the cooling system on operation in order to aim at preventing occurrence of freezing and dewing, to allow a stand-by electronic system to smoothly start its operation, thereby it is possible to aim at saving energy.
According to a first aspect of the present invention, there is provided a cooling apparatus including a cooling pipe for feeding liquid coolant direct below or around a heat generating element and a heat-exchanger unit for expelling heat from the liquid coolant which has absorbed heat from the heat generating element, and externally emitting the heat, the liquid coolant having a low temperature being repeatedly circulated through the cooling pipe, wherein the cooling pipe is flattened in part so as to form flattened parts which are located right below the heat generating elements in the vicinity of the same in order to increase a planar projection area of the heat generating element, thereby the generated heat is efficiently transmitted to the liquid coolant.
Further, the cross-sectional area of the flattened parts of the cooling pipe is set to be smaller than that of parts other than the former so as to increase the velocity of the liquid coolant in order to enhance the cooling efficiency.
Further, the flattened parts of the cooling pipe are integrally incorporated with parts other than the former, thereby it is possible to prevent leakage of the liquid coolant.
Further, the cooling pipe is flattened only in required parts so as to restrain pressure loss.
Further, each of the flattened parts of the cooling pipe is fixed to one surface of a substrate having the other surface, opposite to the former, which is attached thereto with the heat generating element, through the intermediary of a heat conduction block, and accordingly, the cooling pipe can be attached on one surface side of the substrate.
According to the first aspect of the present invention, with the use of the above-mentioned measures, since the part of the cooling pipe attached in the vicinity of the heat generating element, is formed into a flattened shape, the planar contact surface area with respect to the heat generating element can be increased while the heat flux can smoothly enter the cooling pipe, normal to the latter, thereby it is possible to efficiently transmit heat to the liquid coolant.
Further, the part of the cooling pipe attached to the heat generating element is formed into a flattened shape, the velocity of the fluid is increased so as to enhance the heat transmission rate, thereby it is possible to enhance the thermal efficiency of the cooling pipe.
Further, the cooling pipe is formed from its inlet to its outlet from a single pipe, and is formed into flattened shapes only in parts in the vicinity of heat generating elements, and accordingly, the pressure loss can be restrained to be minimum, thereby it is possible to miniaturize a pump for feeding liquid coolant and to minimize power consumption.
Further, the cooling pipe is formed from its inlet to its outlet, from a single pipe, and accordingly, no joints are present therein, thereby it is possible to substantially eliminate leakage of liquid coolant, and to aim at enhancing the quality and reliability of the cooling apparatus.
Further, the part where the cooling pipe is formed into a flattened shape, is jointed thereto with a heat conduction block having a satisfactory heat transmission, with the use of a brazing material or the like, and accordingly, the cooling pipe can be fixed to a circuit board on the side remote from the electronic part as the heat generating element attached thereto. Thus, the cooling pipe can be attached with no affection upon the electronic parts mounted on the circuit board, thereby it is possible to enhance the workability of assembly of the electronic system. That is, since the circuit board on which the electronic parts are mounted, is isolated from the cooling pipe, thermal deformation caused during assembly of the cooling pipe can be prevented from being transmitted to the circuit-board side.
According to a second aspect of the present invention, there is provided a cooling apparatus comprising a heat-exchanger unit for expelling heat which has been absorbed from heat generating elements in an electronic system by cooling the heat generating elements, a pump for circulating liquid coolant for cooling the heat generating elements, a tank for reserving the liquid coolant, cooling pipes through which the liquid coolant flows, and around which the heat generating elements are mounted, and pipe line elements for connecting the cooling pipe and the like, the liquid coolant being fed and circulated, the heat-exchange capacity of the heat-exchanger unit is controlled in accordance with an atmospheric temperature.
Further, the range where the operating temperature of the electronic parts which generates heat in the electronic system varies, depending upon variation in the atmospheric temperature, is made to be narrower, and accordingly, the stability and the reliability of operation of the electronic parts can be enhanced. If the temperature variation range in the electronic system is as narrow as possible, the necessity of anti-freezing fluid can be eliminated, and as a result, the pipe line including the cooling pipe through which the liquid coolant is circulated can be prevented from being deteriorated due to corrosion or the like, thereby it is possible to further enhance the reliability.
Further, the heat-exchange capacity is controlled in accordance with an atmospheric temperature detected by a temperature detector provided in an inlet port for introducing the atmospheric air while whether at least either one of a temperature of liquid coolant detected by a temperature detector provided in the electronic system and a temperature of an electronic part serving as the heat generating element, detected by a temperature detector provided to the electronic part is within a safe operation range or not is confirmed. Further, the rotational speed of a motor for driving a fan for introducing the atmospheric air into the heat-exchanger unit, or the turn-on and -off rate of an input power source may be controlled in order to control the heat-exchange capacity of the heat-exchanger unit. Further, the heat-exchange capacity can be controlled at four stages, that is, the heat-exchange capacity is relatively high, middle, low and extremely low due to the operation of the fan for heat-exchange is stopped, in accordance with an atmospheric temperature.
A third aspect of the present invention is to provide a cooling apparatus comprising two cooling systems each including a heat-exchanger unit which expels heat absorbed from an electronic system through the intermediary of a cooling pipe, a pump for circulating liquid coolant for cooing the electronic system, a tank for reserving the liquid coolant, pipe line elements for connecting the former, and a damper for taking a part of the expelled heat into a fan duct of the heat-exchanger unit, the electronic system being cooled through the intermediary of the cooling pipe, one of the two cooling system being normally operated and the other one of them being stand-by.
Further, it has a temperature measuring means and a control means for controlling the heat-exchanger unit in response to a signal from the temperature measuring means.
That is, according to the third aspect of the present invention, the cooling apparatus does not expel all heat absorbed by the heat-exchanger unit during operation, but a part of the heat is selectively taken into the fan duct through an opening opened by the damper so as to raise the temperature in the housing of the electronic system, thereby it is possible to prevent occurrence of dewing in the electronic system and freezing of the liquid coolant.
According to a fourth aspect of the present invention, there is provided a highly efficient liquid cooling apparatus comprising two liquid cooling systems each including a heat-exchanger unit for expelling heat absorbed from heat generating elements in an electronic system during cooling of the heat generating elements, a pump for circulating liquid coolant for cooling the heat generating element, a tank reserving the liquid coolant, a cooling pipe through which the coolant flow and in the vicinity of which the heat generating elements are mounted, and pipe line elements for connecting the former, wherein the tank is commonly used for both liquid cooling systems.
Further, according to the fourth aspect of the present invention, the commonly used tank may be provided therein with a partition panel for holding in the tank the liquid coolant so as to feed the liquid coolant into the two liquid cooling systems, independent from each other. The partition panel in the tank partitions the lower part of the inside of the tank into two spaces which are isolated from each other in the lower part of the tank, but which are opened to each other in the upper part of the tank. Thus, the liquid coolant in the tank flows freely in the upper part of the tank, thereby it is possible to feed the liquid coolant above the upper edge of the partition panel into either of the two cooling systems.
Further, according to the fourth aspect of the present invention, an inlet pipe line to the tank has a port provided at a position which is relatively near to the partition panel, at a height which is slightly lower than the upper edge of the partition panel while an outlet pipe line from the tank has a port provided at a position which is relatively far from the partition panel, and which is in the bottom part of the tank. With this arrangement, the liquid coolant above the upper edge of the partition wall can flow into either of the two liquid cooling systems, efficiently due to the kinetic energy of the liquid coolant flowing through the ports of the pipe lines.
According to the fourth aspect of the present invention, in the case of such an operation mode that the heat generating element in the first one of the two liquid cooling systems do not generate heat but while those in the second one of the them generate heat, the first cooling system allows the liquid coolant to continuously flows therethrough while the first cooling system allows the liquid coolant to intermittently flow therethrough or stop the flow of the liquid coolant, thereby it is possible to prevent occurrence of dewing or freezing. Further, in the case of the circulation of the liquid coolant, the operation of the cooling fan of the heat-exchanger unit in the second system may be rested.
Further, in the liquid cooling apparatus according to the fourth aspect of the present invention, in the case of the circulation of the liquid coolant for expelling heat absorbed from the heat generating element in the electronic system during cooling of the heat generating elements, the operation of the cooling fan of the heat-exchanger unit in the second cooling system may be rested.
Explanation will be hereinbelow made of preferred embodiments of the present invention with reference to the accompanying drawings.